Former England captain Andrew Strauss said Friday it was important for the side's Ashes prospects that star batsman Kevin Pietersen regained full fitness.

Pietersen is currently sidelined with a knee problem and in his absence England struggled to 232 all out in the first innings of the first Test against New Zealand at Lord's.

Strauss retired from all cricket following a 2-0 series defeat by South Africa last year where Pietersen was dropped from the team for sending text messages critical of his captain to Proteas players.

But Strauss, who succeeded Pietersen as England captain, always insisted the texts had not hastened his retirement.

And on Friday, in an interview with Sky Sports at Lord's, the former opening batsman said Pietersen was the "best player" he'd played with .

"The vast majority of the time he's very easy to manage because he works really hard, he's very professional in the way he goes about his business," Strauss said.

"And we all know what he brings. As far as I'm concerned he's the best player I've ever played with, in terms of sheer talent, in terms of the ability to take the game away from the opposition -- he's outstanding," added Strauss, set to join five other ex-England captains in the Sky commentary box for the Ashes.

"But you know what you're getting with someone like Kevin, obviously. He has got a big ego, and he likes to be the centre of attention and that's always going to rub some people up the wrong way.

"But that is one of a challenges of captaincy -- bringing a disparate group of people together and making sure they all have a common purpose."

Former opening batsman Strauss added: "I think we've seen in this Test how much he (Pietersen) can change the tempo -- I think we're missing him in this game...It's important for England he's fit."

Three-times an Ashes-winner, Strauss led England to a 3-1 series victory the last time cricket's oldest rivals met in Australia in 2010/11.

In July, England will begin their bid for a third Ashes triumph in a row -- something they last managed back in the 1950s.

However, Strauss said an England team now captained by his former opening partner Alastair Cook would have their work cut out against Australia's pacemen.

"They have got a really a really good bowling attack -- it will be interesting to see how Mitchell Starc goes over here.

"But the area where they are weakest, you'd say, is their batting.

"Some of these guys haven't played much in England before and there are a lot of left handers in there.

"(England off-spinner) Graeme Swann will be licking his lips at the possibility of playing these guys on turning wickets.

"It's going to be closely contested series - Ashes always are and this one will be no different."